The present disclosure relates generally to systems and methods for monitoring and controlling polymerization systems.
As chemical and petrochemical technologies have advanced, the products of these technologies have become increasingly prevalent in society. In particular, as techniques for bonding simple molecular building blocks into longer chains (or polymers) have advanced, the polymer products, typically in the form of various plastics, have been increasingly incorporated into various everyday items. For example, polyolefin polymers, such as polyethylene, polypropylene, and their copolymers, are used for retail and pharmaceutical packaging, food and beverage packaging (such as juice and soda bottles), household containers (such as pails and boxes), household items (such as appliances, furniture, carpeting, and toys), automobile components, pipes, conduits, and various other consumer and industrial products.
One benefit of polyolefin construction is that it is generally inert and non-reactive with goods or products with which it is in contact, as well as with the surrounding environment. This property allows polyolefin products to be used in many residential, commercial, and industrial contexts, including food and beverage storage and transportation, consumer electronics, agriculture, shipping, and vehicular construction. The wide variety of residential, commercial and industrial uses for polyolefins has translated into a substantial demand for raw polyolefin which can be extruded, injected, blown or otherwise formed into a final consumable product or component.
The raw polyolefin is typically produced in bulk by petrochemical facilities, which have ready access to monomers (e.g., ethylene) and comonomers, such as alpha olefins (e.g., 1-butene or 1-hexene or 1-octene), that serve as the molecular building blocks of the polyolefins to be produced. In some polymerization processes, the components used for polymerization, such as a monomer, a comonomer, and a catalyst facilitating polymerization of the monomer and comonomers, are solvated and/or suspended in a diluent. In these cases, the catalyst and the polyolefin formed as a result of the polymerization reaction are typically suspended in the diluent to form a slurry. The polymerization reaction itself may be performed in systems, such as a polymerization reactor, where temperature and pressure can be regulated to produce polyolefins having certain desired properties.
However, in some circumstances, during standard operation, the polymerization reactor may “foul,” an event that occurs when the polymerized product formed adheres on the inside of the reactor walls, or when the product cannot be maintained as a slurry and solidifies within the reactor. Such a foul may result in a loss in heat transfer, such as due to a reduction in circulation or reduced efficiency at a heat exchanger interface, which may impair or completely negate the capacity to maintain the desired temperature within the reactor. A reactor foul may also result in a reduction in the circulation of the reactor contents and/or in a variation from the desired percent solids (measured by volume or by weight) of the reactor slurry. To the extent that a change in the operation of a reactor, such as in a fouling situation, may result in deviations from the desired reaction conditions, the polymer product produced during such a reactor foul may not meet the desired specifications; that is, the product may be “off-spec.” In extreme or runaway fouling situations, control of the reaction may be lost entirely, and the reactor may become plugged with polymer, requiring weeks to clear, during which time the reactor may not be operated. Therefore, a system that monitors reactor contents and adjusts a feed of polymerization components to prevent or minimize the occurrence of fouling is desired.
Further, due to their potential for fouling, reactors are typically operated with some headroom to avoid fouling conditions because it is difficult to monitor exact conditions within the reactor. For example, conditions within the reactor may often be inferred based on operational parameters (e.g., temperature and/or pressure). It is now recognized that it would be desirable to be able to more accurately evaluate polymerization conditions to enable enhanced polymer production and improved control over the polymerization process itself.
While the inventions disclosed herein are susceptible to various modifications and alternative forms, only a few specific embodiments have been shown by way of example in the drawings and are described in detail below. The figures and detailed descriptions of these specific embodiments are not intended to limit the breadth or scope of the inventive concepts or the appended claims in any manner. Rather, the figures and detailed written descriptions are provided to illustrate the inventive concepts to a person of ordinary skill in the art and to enable such person to make and use the inventive concepts.